【javascript】配列のシャッフル2 - Qiita

//要素の入れ替え関数 const swap = (a,i,j) => ( [a[i], a[j]] = [a[j], a[i]], a ); //reduceの内部処理 const reducer = (p,_,i,$,m=p.length-i) => swap(p, m-1, Math.floor(Math.random() * m)); //本体 const shuffleArray = arr => arr.reduce(reducer, arr.slice()); console.log(shuffleArray( [...Array(15).keys()]) ); const shuffleArray = arr => arr.reduce((p,_,i,$,m=p.length-i,r=Math.floor(Math.random()*m--)) => ([p[m], p[r